• Journal of the Korean Vacuum Society
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• v.7 no.s1
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• pp.50-56
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• 1998

Ion beam assisted deposition (IBAD) was successfully used to produce a dense and ultra-adherent Hydroxyapatite (HA) film on titanium alloy and alumina. Recently it is also proved that the HA coatings on alumina substrate treated with 20 ppm $AgNO_3$ had the structure of $(Ag, Ca)_10(PO_4)6(OH)_2$, which exhibited excellent antimicrobial effects. The present paper aims to morphlogically characterize the adhesion of macrophages on newly developed Ag-HA coated alumina and Ti6A14V substrates and to evaluate the biocompatibility of the coatings in vitro. It can be found that the cell number on alumina of the concentration of $AgNO_3$ in the treatment, the cell number on Ag-HA coatings decreased. Up to 20 ppm $AgNO_3$ by Ag-treatment, the morphological development of the cells on Ag-HA coating was similar to that of the cells on HA coating, suggesting the biotolerance of the Ag-HA coatings.

• The Korean Journal of Food And Nutrition
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• v.1 no.2
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• pp.50-55
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• 1988

B-Amylase was obtained from sweet potato extract in a crystalline state by dialysis against water after precipitated with acetone according to the method reported previously followed by DEAE Sephadex A-50 ion exchange chromatography plus gel chromatography of Sephadex G-200. The purified enzyme was homogeneous by SDS PAGE. The efforts had done to remove the miner bands in SDS PAGE by Sephadex G-200 gel chromatography, DATE Sephadex A-50 ion exchange chromatography. isoelectrophocusing, affinity chromatography, hydroxyapatite chromatography, recrystallizstion and HPLC on a column of TSK gel SW 3000 but have given any result. But, N -terminal amino acid of the enzyme was revealed mainly alanine and trace of glycine and glutamic acid. Therefore, it seems that the miner bands in SDS PAGE have a role of subunit.

• Korean Journal of Microbiology
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• v.25 no.4
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• pp.297-297
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• 1987

A $C_{1}$ enriched cellulase fraction was separated from culture filtrate of anaerobic Clostridium thermocellum by hydroxyapatite column chromatography. The separated fraction showed strong synergistic action with $C_{x}$ component (endo-$\beta$-1, 4-glucanase) in digestion of crystalline cellulose, similar to the other aerobic cellulolytic microorganisms. Unlike the $C_{x}$ component the $C_{1}$ enriched fraction was rapidly inactivated by oxidation at the atmospheric condition. The enzyme activity was significantly enhanced by the addition of reducing agents, especially $\beta$-mercaptoethanol, which indicates that a $C_{1}$ component has a lot of sulfhydryl groups essential for the enzyme activity. The effect of metal ions on $C_{1}$ activity was also investigated. The $C_{1}$ fraction was found to be thermally stable compare to endo-$\beta$-1,4-glucanase. Optimal temperature and pH were found to be 60.deg.C and 6.0, respectively.

• Journal of the Korean Vacuum Society
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• v.6 no.S1
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• pp.27-33
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• 1997

Recently ion beam assistant deposition (IBAD) was successfully used to produce a dense ultra-adherent and pinhole-free hydroxyapatite (HAp) layer on alumina substrate. After that the HAp-coated alumina was immersed in 20ppm and 100ppm $AgNO_3$ solution at room temperature for 48 hours to carry out the ions exchange between $Ag^+\;and\;Ca^+$ in HAp. The obvious antimicrobial effect against E.Coli, P. Aeruginosa and S. Epidermidis was observed in the samples treated with 20ppm $AgNO_3$ Solution, In contrast to this the untreated samples did not show any bactericidal effect. Scanning electron microscope(SEM) study showed that Ag homogeneously distributed on the surface. X-ray diffraction (XRD) demonstrated that the surface structure in the samples without Ag was HAp whereas with Ag is HAp and AgCaP. It appears that silver ions exchange with calcium ions in HAp does not cause significant changes in the structure of HAp coatings.

• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2499-2507
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• 2012

A novel and convenient electrochemical method has been developed for sensitive determination of melamine (MEL) using ascorbic acid (AA) as the recognition element. The working electrode employed in this method was modified with the nanocomposite of hydroxyapatite/carbon nanotubes to enhance the current signal of recognition element. The interaction between MEL and AA was investigated by fourier transform infrared spectroscopy and cyclic voltammetry, and the experimental results indicated that hydrogen bonding was formed between MEL and AA. Because of the existing hydrogen bonding and electrostatic interaction, the anodic peak current of AA was decreased obviously while the non-electroactive MEL added in. It illustrated that the MEL acted as an inhibitor to the oxidation of AA and the decreasing signals can be used to detect MEL. Under the optimal conditions, the decrease in anodic peak current of AA was proportional to the MEL concentrations ranging from 10 to 350 nM, with a detection limit of 1.5 nM. Finally this newly-proposed method was successfully employed to detect MEL in infant formula and milk, and good recovery was achieved.

• Advances in materials Research
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• v.4 no.3
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• pp.145-164
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• 2015

Biodegredable and injectable nanocomposites based on polypropylene fumarate (PPF) as unsaturated polyester were prepared. The investigated polyester was crosslinked with three different monomers namely N-vinyl pyrrolidone (NVP), methyl methacrylate (MMA) and a mixture of NVP and MMA (1:1 weight ratio) and was filled with 45 wt% of hydroxyapatite (HA) incorporated with different concentrations of chemically treated natural bone powder (NBP) (5, 10 and 15 wt%) in order to be used in treatment of orthopedics bone diseases and fractures. The nanocomposites immersed in the simulated body fluid (SBF) for 30 days, after the period of immersion in-vitro bioactivity of the nanocomposites was studied through Fourier transform infrared (FTIR), scanning electron microscope (SEM), energy dispersive X-ray (EDX) in addition to dielectric measurements. The degradation time of immersed samples and the change in the pH of the SBF were studied during the period of immersion.

• BMB Reports
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• v.29 no.5
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• pp.436-441
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• 1996

The palmitoyl acyl carrier protein (ACP) specific thioesterase (EC 3.1.2.14) from Iris pseudoacorus was purified and characterized. The thioesterase which was very unstable in relatively high salt concentrations was eluted using a co-gradient of Triton X-100 and low concentration of KCl or Na-phosphate from Q-Sepharose, DEAE-Sepharose, and hydroxyapatite chromatography. SDS-PAGE analysis showed a single band with a molecular weight of 35,000. The native molecular weight of approximately 37,000 was estimated by Sephacryl S-200 chromatography, indicating that the enzyme is a monomer. The thioesterase activity was inhibited about 75% and 50% by N-ethylmaleimide (2 mM) and phenylmethylsulfonyl fluoride (2 mM). respectively. The N-ethylmaleimide-inactivation was protected by sodium palmitate but the inactivation with phenylmethylsulfonyl fluoride was not protected. Oxidation of thiols by 2 mM 5.5'-dithio-bis-(2-nitrobenzoic acid) resulted in 65% inactivation of the enzyme. These results suggest that a cysteinyl residue is essential to the catalytic reaction of the enzyme. The enzyme activity was increased by sodium citrate and also by $Cu^{2+}$

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.1
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• pp.32-39
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• 2000

The purpose of this study was to assess the cariogenic potential of five infant formulas in vitro. as compared with 10% sucrose solution and whole bovine milk. Buffering capacities were determined by the amount of 0.1 N lactic acid consumed to titrate the 50ml specimen solutions to pH 4.0. The pH of the specimen solution inoculated by Streptococcus mutans was measured by pH meter and the surface microhardness of primary tooth enamel immersed in the specimen solution was measured by the microhardness tester, before and after 48 hours incubation. Also, the solubility of calcium from synthetic hydroxyapatite was evaluated by atomic absorption spectrophotometer The buffering capacity of infant formulas was higher than that of sucrose solution and lower than that of milk, and there were significant differences among infant formulas(P<0.01). The average pH of infant formulas after 48 hours incubation was lower than that of sucrose solution and milk, and there was significant difference between infant formulas and milk(P<0.05). There were no signifiant differences among oops in the microhardness change of primary tooth enamel and in the amount of dissolved calcium ion from synthetic hydroxyapatite after incubation with Streptococcus mutans. In conclusion, infant formulas seemed to fulfill the basic requirments to cause dental caries in primary teeth, and there were significant differences of cariogenic potential among infant formulas. Cooperative efforts of dentistry and manufacturers to reduce the cariogenic potential of infant formulas would be necessary to prevent the early childhood caries in children.

• KSBB Journal
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• v.19 no.4
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• pp.301-307
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• 2004

The characteristics of the a-amylase of Aspergillus coreanus NR 15-1 isolated from traditional Korean Nuruk have been carried out. The a-amylase of A. coreanus NR 15-1 was purified by ammonium sulfate precipitation followed by column chromatographies on CM-cellulose, DEAE-cellulose, Sephadex G-100 gel filtration and hydroxyapatite. The a-amylase was purified 78-fold with a yield of 8.7%. The molecular weight of the a-amylase was estimated to be 49 kDa by Sephadex G-100 gel filtration and 51 kDa by SDS-polyacrylamide gel eletrophoresis. These experimental results suggested that the purified enzyme might be monomer. The enzyme was stable between pH 4 and 11. The optimum pH was 5.0. The optimum temperature for enzyme was 45$^{\circ}C$ and the enzyme was stable up to 50$^{\circ}C$. The enzyme was significantly inhibited by 1 mM N-bromosuccinimide. These results suggested that tryptophan residue was involved in the active site of a-amylase. The enzyme was identified as a-amylase because the reaction products of soluble starch hydrolyzed by the purified enzyme was oligosaccharide by thin layer chromatography.

• Journal of dental hygiene science
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• v.16 no.1
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• pp.70-76
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• 2016

The objective of this study was to fabricate hydroxyapatite (HA) containing titania layer by HA blasting and anodization method to obtain advantages of both methods and evaluated biocompatibility. To fabricate the HA containing titania layer on titanium, HA blasting treatment was performed followed by microarc oxidation (MAO) using the electrolyte solution of 0.04 M ${\beta}$-glycerol phosphate disodium salt n-hydrate and 0.4 M calcium acetate n-hydrate on the condition of various applied voltages (100, 150, 200, 250 V) for 3 minutes. The experimental group was divided according to the surface treatment procedure: SM (simple machined polishing treatment), HA, MAO, HA+MAO 100, HA+MAO 150, HA+MAO 200, HA+MAO 250. The wettability of surface was observed by contact angle measurement. Biocompatibility was evaluated by cell adhesion, and cell differentiation including alkaline phosphatase activity and calcium concentration with MC3T3-E1 cells. The porous titanium oxide containing HA was formed at 150 and 200 V. These surfaces had a more hydrophilic characteristic. Biocompatibility was demonstrated that HA titania composite layer on titanium showed enhanced cell adhesion, and cell differentiation. Therefore, these results suggested that HA containing titania layer on titanium was improved biological properties that could be applied as material for dental implant system.